I came to believe that in order to get points for "marksman headshot", all you had to do is a headshot at a distance of over 100 meters (or yards?). But I have an impression, that I'm not getting these points while not using a sniper rifle (eg. for longshot with LMG).

A marksman headshot is the first shot in the head from a greater distance than usual. How much, I really don't know. You can get it with any weapon with sufficient range.

In order to make the shot count as marksman headshot, it needs to be the first shot and it must be a head-shot.
If you shoot multiple bullets and hit the body before the head, no matter how far he is you are only getting the normal headshot points.

To my knowledge the marksman headshot bonus can only be achieved in the sniper class. Its basically extra points for killing people that are quite far away with a headshot.

To get the bonus your target has to be over 100 meters away and then every meter over 100 will get you another point. So if you killed someone 101 meters away you would get a +1 Marksman headshot, killing someone 200 meters away will give you a +100 marksman headshot bonus etc.

As far as I am aware the highest bonus you can get from this is +500 (although I cant confirm this because thats only from personal experience and never getting higher than that).

A little tip for achieving these is to hold down the fire button once you have fired the sniper rifle - this will keep the scope open so you can follow the path of the bullet and how much it dips. This will make adjusting for the second shot much easier.

ok, how about Recon class with M-14 EBR -- will I still get bonus?
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vartecMar 6 '11 at 17:13

has to be with a sniper class weapon i.e. not the weapons that can be used in any class.
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Craig PilgrimMar 6 '11 at 19:15

1

I can clarify score a bit. You get 50 score by default plus 1 for every meter above 100m. So for 101m headshot you will get 51 marksman bonus. Also 500 points seems like the limit.
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sergMar 11 '11 at 18:02